Due to the aging society, patients with dementia have been increasing every year. There are various types in dementia, and it is necessary to distinguish the types at diagnosis to offer proper treatment.
In order to meet the demands above, recently, it becomes possible to obtain information regarding a state of the brain by nuclear medicine scanning such as SPECT (Single Photon Emission Computed Tomography) and PET (Positron Emission Tomography), or CT (Computerized Tomography) and MRI.
Consequently, it has been revealed that the phenomenon, such as blood flow and metabolism of a specific region of the brain decreases and atrophy of tissue thereof occurs, varies according to the types of disease, and thus a measurable assessment method for the above has been sought.
For example, decreasing of blood flow and metabolism in a certain portion of the brain can be examined by comparing SPECT or PET images.
Furthermore, regarding atrophy of tissue, it is possible to determine whether an abnormality is present by obtaining the volume of a specific region from an MRI image and comparing relative scales thereof.
As an assessment method of atrophy of tissue by use of such a brain image, VBM (Voxel Based Morphometry) is known. VBM is performed by processing a brain image obtained by imaging the head of a subject, with voxel (an image element in three dimensions) basis, (for example, see the patent document 1).
The VBM method is an effective assessment method for identifying the Alzheimer's disease, and it is reported that the diagnostic capability thereof for identifying an individual with the Alzheimer's disease from normal individuals is 87.8% (see the non-patent document 1).